The fabrication of high-quality ultra thin (~20 micron) diamond crystals targets for 9 GeV highly polarized photon beams is an outstanding challenge. Current state of the art polishing/thinning techniques are not successful in thinning single crystal diamond to such dimension because of its extreme hardness and chemical inertness. These techniques create significant stresses surface and sub-surface damage that limits the final thickness to approximately 100m. Sinmat proposes to develop a novel gentle chemical mechanical planarization technology that can rapidly thin and polish diamond crystal targets to sub 20 micron without inducing damage or stress in the crystal. Sinmat estimates that this process can thin diamond at rates greater than 3 m/hr without causing stress or subsurface damage. Commercial Applications and Other Benefits: The ability to create ultra smooth and defect free diamond surface has significant application in nuclear instrumentation and detector research, electronics and mechanical application. Defect-free ultra- Smooth diamond films and crystals can be used as Bremsstrahlung radiators for generation of linearly polarized photon beams, dose detector for synchrotron and other radiation sources, radiation hardness devices, and as heat spreaders for advanced electronic applications.